Decreased Interfacial Tension of Demixed Aqueous Polymer Solutions due to Charge

Vis, Mark; Peters, Vincent F. D.; Blokhuis, Edgar M.; Lekkerkerker, H. N. W.; Erné, Ben H.; Tromp, R. Hans

doi:10.1103/physrevlett.115.078303

Cited by 33 publications

(36 citation statements)

References 48 publications

(65 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Phase diagrams for the demixing of aqueous solutions of dextran (uncharged polymer) and fish gelatin (polyelectrolyte), measured at polyelectrolyte charges z = +20 (9 mM salt) and z = +5 (5 mM salt). 15 The points are the experimentally measured compositions of the coexisting phases and the solid lines are a guide to the eye. The binodal is shifted away from the origin upon an increase of z.…”

Section: ■ Resultsmentioning

confidence: 99%

Effects of Electric Charge on the Interfacial Tension between Coexisting Aqueous Mixtures of Polyelectrolyte and Neutral Polymer

et al. 2015

Self Cite

View full text Add to dashboard Cite

Upon demixing, an aqueous solution of a polyelectrolyte and an incompatible neutral polymer yields two phases separated by an interface with an ultralow tension. Here, both in theory and experiment, we study this interfacial tension in detail: how it scales with the concentrations of the polymers in the two phases and how it is affected by the interfacial difference in the electrical potential. Experiments are performed on an aqueous model system of uncharged dextran and charged nongelling gelatin. The experimental tension scales to the power ∼3 with the tie-line length in the phase diagram of demixing, in agreement with mean-field theory where space is filled with a binary mixture of polymer blobs. The interfacial electrical potential difference is experimentally found to decrease the interfacial tension in a way that is consistent with Poisson−Boltzmann theory inspired from Frenkel and Verwey−Overbeek. ■ INTRODUCTIONWhen aqueous solutions of polymers are mixed, phase separation is a commonly observed phenomenon. 1−4 It yields phases that differ in the concentrations of the polymers. The interface between the phases is not abrupt, but there are gradients in the relative composition and the total concentration of the polymers. A particularity of phase separating solutionsas opposed to phase separated blendsresults from the osmotic compressibility of the solutions: compared to the bulk phases, the interfacial region is diluted by uptake of solvent. 5 In the case of charged polymers, there is also an interfacial gradient in the electric charge density, corresponding to an interfacial electric potential step. This is the so-called Donnan potential, 6,7 and its effect on the interfacial tension is the subject of this paper.The main conditions for phase separation are a sufficient concentration and a sufficient degree of polymerization. These two factors often make the unfavorable mixing enthalpy dominate over the small mixing entropy of two types of polymer. Phase separation is also affected by the presence of charge on the polymers. 8 For instance, when one of the polymers is charged and the other is uncharged, phase separation becomes entropically more unfavorable due the accumulation of counterions in one of the phasesnecessary for charge neutrality. In order to increase entropy, the positive and negative salt ions spread across the interface to different extents; the buildup of charge separation halts the spreading.The accompanying electric potential difference is the Donnan potential. It has the same origin as the well-known membrane potential found in living cells and dialysis membranes. However, in our case, the charged interface is formed spontaneously and in equilibrium with the bulk phases; moreover, the interfacial electric potential step is relatively small, typically less than 10 mV, 9 as compared to 40−60 mV for the membranes of living cells.The electric interfacial potential step contributes negatively to the interfacial tension due to the spontaneous formation of interfacial electrical double layer...

show abstract

Section: ■ Resultsmentioning

confidence: 99%

Effects of Electric Charge on the Interfacial Tension between Coexisting Aqueous Mixtures of Polyelectrolyte and Neutral Polymer

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…For the experiments in this work, the demixing polymer solutions were composed of dextran (average molar mass 150 kDa from Leuconostoc bacteria, purchased from Sigma Aldrich) and cold water fish gelatin (non gelling at room temperature, from Norland Products, provided by Fibfoods, Harderwijk, The Netherlands) at native pH 5.8 and salinity corresponding to 25 mM of NaCl. Gelatin and dextran mixed in water at proper concentration spontaneously demix forming dextran and a gelatin phases with well characterized phase equilibria [18][19][20]. The system studied has 10/10 %w/w dextran/gelatin and has equilibrium concentrations 17/0.1 and 1.2/22 for the dextran and gelatin phase, respectively, and a tie line length T T L = 27 %w/w.…”

Section: Methodsmentioning

confidence: 99%

Colloidal Particle Adsorption at Water-Water Interfaces with Ultralow Interfacial Tension

et al. 2018

Self Cite

View full text Add to dashboard Cite

Using fluorescence confocal microscopy we study the adsorption of single latex microparticles at a water-water interface between demixing aqueous solutions of polymers, generally known as a water-in-water emulsion. Similar microparticles at the interface between molecular liquids have exhibited an extremely slow relaxation preventing the observation of expected equilibrium states. This phenomenon has been attributed to "long-lived" metastable states caused by significant energy barriers ΔF∼γA_{d}≫k_{B}T induced by high interfacial tension (γ∼10^{-2} N/m) and nanoscale surface defects with characteristic areas A_{d}≃10-30 nm^{2}. For the studied water-water interface with ultralow surface tension (γ∼10^{-4} N/m) we are able to characterize the entire adsorption process and observe equilibrium states prescribed by a single equilibrium contact angle independent of the particle size. Notably, we observe crossovers from fast initial dynamics to slower kinetic regimes analytically predicted for large surface defects (A_{d}≃500 nm^{2}). Moreover, particle trajectories reveal a position-independent damping coefficient that is unexpected given the large viscosity contrast between phases. These observations are attributed to the remarkably diffuse nature of the water-water interface and the adsorption and entanglement of polymer chains in the semidilute solutions. This work offers some first insights on the adsorption dynamics or kinetics of microparticles at water-water interfaces in biocolloidal systems.

show abstract

“…The capillary length, in turn, was found by analyzing the deformation of the static interfacial profile near a vertical wall, 32 which has a shape given by 33 where x denotes the distance to the vertical wall, z denotes the elevation of the profile above the level infinitely far from the wall, and h ≡ z ( x = 0) denotes the contact height. See refs ( 13 ) and ( 14 ) for an extended description.…”

Section: Methodsmentioning

confidence: 99%

Interfacial Tension of Phase-Separated Polydisperse Mixed Polymer Solutions

et al. 2017

Self Cite

View full text Add to dashboard Cite

Aqueous two-phase systems provide oil-free alternatives in the formulation of emulsions in food and other applications. Theoretical interpretation of measurements on such systems, however, is complicated by the high polydispersity of the polymers. Here, phase diagrams of demixing and interfacial tensions are determined for aqueous solutions of two large polymers present in a mass ratio of 1:1, dextran (70 kDa) and nongelling gelatin (100 kDa), with or without further addition of smaller dextran molecules (20 kDa). Both in experiments and in calculations from Scheutjens–Fleer self-consistent field lattice theory, we find that small polymers decrease the interfacial tension at equal tie-line length in the phase diagram. After identifying the partial contributions of all chemical components to the interfacial tension, we conclude that excess water at the interface is partially displaced by small polymer molecules. An interpretation in terms of the Gibbs adsorption equation provides an instructive way to describe effects of polydispersity on the interfacial tension of demixed polymer solutions.

show abstract

Decreased Interfacial Tension of Demixed Aqueous Polymer Solutions due to Charge

Cited by 33 publications

References 48 publications

Effects of Electric Charge on the Interfacial Tension between Coexisting Aqueous Mixtures of Polyelectrolyte and Neutral Polymer

Effects of Electric Charge on the Interfacial Tension between Coexisting Aqueous Mixtures of Polyelectrolyte and Neutral Polymer

Colloidal Particle Adsorption at Water-Water Interfaces with Ultralow Interfacial Tension

Interfacial Tension of Phase-Separated Polydisperse Mixed Polymer Solutions

Contact Info

Product

Resources

About